Empirical attenuation relationship for peak horizontal ground acceleration for east of Turkey and Iran

Turkey and Iran, two developing and neighboring counties, are located in one the most seismically active region of world. Up to now, despite the fact that seismotectonic and geological boundaries are not limited to geographical and political borders, studies conducted in both countries were carried out separately for each country. Furthermore, studies conducted up to now face limitation in the number of the data and lack of adequate information regarding local site conditions. In this regard, development of empirical attenuation relationship for peak horizontal ground acceleration for eastern Turkey and the whole Iran is the main goal of the present study.Data set used for the present study consist of acceleration time histories gathered from strong motion networks of Iran and Turkey as well as the outcomes of the researches related to measurement and investigation of local site conditions which were published by the national and international institutes.Primarily, in order to prepare a catalogue for the necessary analyses strong motion data have been processed using Utility Software for Data Processing (USDP) to adjust the data for different types of noises as much as possible. Furthermore, hypocentral distances have been calculated using P-S waves arrival time of each record or using ARCGIS software. Magnitude of each event has been adopted from CMT catalogue. Secondly, by use of the prepared data set, regression analysis and genetic algorithm analysis were conducted for Eastern Turkey, Iran and both countries together. Finally, results were checked using graphical residual analysis.Analyses show that the results of regression analysis and genetic algorithm analysis are very close to each other. Comparisons of result of analysis using data set of Iran and Turkey together and separately show that separate use of data for analysis yields smaller square sum of errors (SSE) and standard deviation (?). Whereas, analysis using data of both country together with each other shows much larger SSE and ? values. And, though sum of residuals are approximately zero, but results are biased for each country. So it is recommended to use the relationships which are developed using separate data set for both countries.